In the past insoles have been made of various materials in an attempt to protect the foot, ankle, knee and various other body structures from the impact associated with walking, running or athletic competition. Among the materials which have been used in the past to fabricate such insoles is the novel elastomer disclosed in U.S. Pat. No. 4,346,205, which is incorporated herein by reference. The material disclosed therein, sold under the trademark SORBOTHANE, is a flexible non-cellular polyurethane of essentially linear structure containing unsatisfied hydroxyl groups, having a compression set less than 15% and preferably less than 5%. At break the material has an elongation of at least 500% and a recovery which is delayed after compression by at least 0.7 seconds. The elastomer disclosed in said patent has a hardness on the Shore 00 scale not exceeding 50, preferably not exceeding 20, and most preferably in the range of 0 to 10. Said patent further suggests that the disclosed elastomeric material may find application in sportswear including athletic shoes, and shock absorber inserts, among others.
Some prior art insoles have been made of essentially homogeneous material of uniform thickness. Others have been made with fabric over an underlying shock absorbing layer. In still others, the underlying shock absorbing layer has been formed with various recesses in the lower surface thereof.